This invention relates generally to local area networks and, more specifically, to token passing in a token ring local area network.
Computers in a computer network often share a limited number of resources. One conventional method of allocating access between shared resources involves passing a xe2x80x9ctokenxe2x80x9d circularly to each computer in the network. The computers agree ahead of time that when using this token protocol, only the computer that has possession of the token may access the resource. A popular example of a network using a token passing algorithm is a token ring network.
Token ring networks are baseband networks, which means that all the transmission capacity (i.e., network bandwidth) of the network media is used by one signal. Because only one signal at a time can be transmitted over the network, multiple computers in a token ring network must not transmit simultaneously. This is accomplished using a token access protocol.
In the token access protocol, computers in the network agree to continuously circulate an information frame to all the computers in the network. When a computer wants to send a message, it waits until it possesses the empty frame, and then modifies the frame by inserting: its message, a destination identifier, and a xe2x80x9ctoken.xe2x80x9d The token may simply be, for example, a bit field in the frame that the inserting computer changes to a 1 to indicate a token is present or a 0 to indicate an empty frame.
The frame is examined by each computer as it is passed around the network. The destination computer copies the message from the frame and changes the token back to zero. The originating computer, when it receives the frame, can verify that its message was received by noticing that the token has been set to zero. The originator then removes the message from the frame and passes the empty frame to the next computer in the network.
Although conventional token ring networks are effective at preventing data collisions, they have disadvantages. In particular, in order to implement a token ring network, all the computers in the network must agree ahead of time on the appropriate protocol to use in passing the message frame. This can be difficult, if, for example, the network administrator wishes to change the protocol of the token ring, as each computer must be updated before the network is operational. It is therefore desirable to improve token ring networks.
Objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purpose of the invention, as embodied and broadly described herein, a first aspect consistent with the present invention includes a method of updating a protocol for controlling a computer network including a plurality of computers, the method comprises the steps of: (1) creating a token object containing methods defining an updated version of the protocol; (2) sequentially passing the token object to each computer in the network; and (3) updating the protocol used by each of the plurality of computers with the methods defining the updated version of the protocol while the token object is present at each computer.
A second aspect consistent with the present invention is directed to a token ring network. The network comprises a plurality of computers coupled together and a token ring object. The token ring object includes methods and data that define a protocol for the token ring network, the token ring object is sequentially transferred to each of the plurality of computers, and when one of the plurality of computers has received possession of the token ring object, it adopts the protocol defined by the token ring object when the protocol defined by the token ring object is different than the protocol in use by the computer.
Further, a third aspect consistent with the present invention includes a method of updating a protocol for controlling a computer network. The method includes the steps of: (1) receiving a token object at a first computer in the network; (2) consulting the token object, and when the token object indicates that a new protocol is to be used to transmit information on the network, updating an older version of the protocol stored at the first computer; and (3) transmitting the token object to a second computer in the network, the second computer being determined based on information in the token object.
Further, an additional aspect consistent with the present invention includes a method of updating a protocol for controlling a computer network. The method includes the steps of: (1) receiving a token object defining a protocol of the network; and (2) sending the object using the protocol defined in the token object.
Still further, an additional aspect consistent with the present invention includes a computer readable memory device containing token including an indication of a protocol to be used when communicating in a network.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments consistent with this invention and, together with the description, help explain the principles of the invention. In the drawings,
FIG. 1 is a high-level diagram of a token ring network;
FIG. 2 is a block diagram illustrating an exemplary embodiment of a computer used in the token ring network;
FIG. 3 is a diagram illustrating an embodiment of a token object consistent with the present invention; and
FIG. 4 is a flow chart illustrating methods consistent with the present invention.